Ore beneficiahon



Sept. 27, 1960 H. v. ATwELL.

om: BENEFICIATION Filed oct. 29, 195s bmw United States "Patent ORE BENEFICIATION Harold V. Atwell, Wappingers Falls, N.Y., assignor to Texaco Inc., a corporalion of Delaware Filed Oct. 29, 1956, Ser. No. 619,038

2 Claims. (Cl. 75-1) This invention relates to an improved method of ore beneciation. More particularly, it is directed to a method for the beneficiation of an oxidic ore of an iron group metal by treatment with carbon monoxide under conditions to effect disintegration of said ore and separation of the disintegrated ore into fractions according to the characteristics of the `disintegrated particles.

High grade ore deposits Which yield their metal values readily are being rapidly consumed and it is necessary for industry to turn to less desirable sources of metal to supply the continued demands. It is likely that in the future it will be necessary to resort -to metal ores which will be increasingly difficult to process. Many ores are uneconomical to process because the ore as found naturally contains relatively little of the desired metal and large quantities of useless gangue. Many of the ores found in nature are hard, tough, and difficult to grind. In order to separate the desired metal constituents, it has been found necessary to grind the ore through at least 100 mesh and often to grind substantially through 325 mesh to permit satisfactory benefciation by the usual processes, for example, magnetic separation, ilotation, and density separation. The cost of grinding metall ores to the neness required becomes inordinantly high when applied to the beneciation of low grade iron ore because of the tonnages of material involved, the cost of maintenance, power consumption, and capital investment.

It is known that the surface of lumps of iron ore may disintegrate in the presence of carbon monoxide containing gases, for example, in the blast furnace process. I have found that iron group metal ores may be treated with carbon monoxide containing gases at a tempera-ture above about 650 F. to effect selective disintegration of the metal component of the ore by forming reaction products internally, so that substantially greater reduction in particle size of the metal component is obtained as compared with the reduction in particle size of the ore gangue. The ore may then be separated into fractions according to particle size to produce a fraction containing a greater concentration of metal component than the original ore. Advantageously, the carbon monoxide-containing gas may be employed to' effect the selective disintegration and separation of beneciated ore concomitantly by grindiing the ore to form iluidizable ore particles consisting of oxide and gangue to permit fluidization, contacting the ground ore with a stream of a carbon monoxide-containing gas at a temperature and gas velocity selected such that the ore particlesv are fluidized, selective disintegration of the metal components of the ore is effected and the fine metal components areentrained in said gas and are removed from the fluid bed in suspension in said gas. Separation of a concentrate of metal may also be effected after the Idisintegration step by other means employing other characteristics of the disintegrated particles. For examp1e, after disintegration with carbon monoxide, the oremay besubjected to gravity separa-tion, flotation, or magnetic separation to effect separation of a metal concentratel from the matrix or less valuable components.

iCC

The vdisintegrated ore may be employed as a catalyst for the reaction of carbon monoxide with hydrogen to form methane, heavier hydrocarbons and oxygenated chemicals. When the :disintegrated ore is used as such a catalyst, the particles comprising the metal components are further altered by the deposition of wax and the formation of metal carbides and these properties may be employed to effect separation of the metal components from the non-metallic parts of the ore. After deposit of a layer of heavy oil or waxy material on the nely divided metal components, the metal components tend to coalesce to the exclusion of the particles of gangue. The metal components may be compacted into suitable lumps, for example, by tumbling in a rotary kiln, With the deposited carbonaceous material serving as a binder. This carbonaceous binder is of further value in that subsequent reduction of the metal components to metallic form is facilitated by the intimate admixture of carbonaceous material,

In w embodiment of the process of this invention, a metal ore is Idisintegrated in a fluidized solids reactor in the presence of carbon monoxide. In this case, disintegration of the particles is effected by the reaction of carbon monoxide with the oxide constituent of the ore internally thereof, and also by the agitation-grinding action within the fluidized bed. Fine particles of higher metal concentration are elutriated from the uidized bed and separated from the gases leaving the fluidized bed. A portion of the iluidized bed is Withdrawn for continuous stripping in a separate elutriation zone to separate a fraction comprising a coarse fraction of reduced metal content.

The process of this invention may be employed in the, beneliciation of ores of iron group metals generally, for example, taconite, hematite, magnetite, gothite, limonite, siderite, pyrite, niccolite, millerite, nickeliferous pyrrhotite, pentlandite, garnierite, smaltite, erythrite and cobal-V rtite. In particular, it may be employed in the processing of iron ores which have heretofore been difficult to process, by conventional means, for example, taconite. The process may be employed to effect disintegration of lumps of ore, for example, about 1" size or may be employed to beneficiate ore which has been ground ne enough to be fluidized, for instance, iine enough to pass a mesh screen. In an embodiment of the invention employing a fluidized ldisintegrator and elutriator, it ispreferred to grind the ore to pass a 100 mesh Tyler Standard Screen. Either carbon monoxide alone or in admixture with other gases may be employed in this process. For example, `synthesis gas produced by the partial oxidation of natural gas and containing about 2 mols of hydrogen for each mol of carbon monoxide may be used. Although gases containing carbon monoxide in any concentration may effect disintegration of iron group metal ores according to the process of this invention, it is desirable that the gas contain substantial quantities of carbon monoxide, for example, about 25 volume percent, to avoid handling excessive quantitiesl of gas. Lower ratios of hydrogen to carbon monoxide, and hence higher car# bon monoxide concentrations, may be obtained by the partial combustion of fuels of lower hydrogen to carbon ratio. For example, fuel oil may be employed to produce a gas by partial combustion having a composition of about 1 mol of hydrogen per mol of carbon monoxide, and coal may be employed to produce a gas having a composition of as low as about 0.5 mol of hydrogen for each mol of carbon monoxide.

A gas rate is selected to maintain a superficial gas t pended solids.) The disintegration of iron group metal ores proceeds at a satisfactory rate while maintaining treating chamber 6 and the ore therein at temperatures between about 650 F. and 1000 F. The upper limit of temperature is `determined by the softening or fusing temperature of the ore and materiails of construction of the apparatus. However, it is preferred to` operate within the temperature range of about 700 to l000 F.

The disintegration step of the process of this invention may be conducted `at relatively low pressures, for example, about atmospheric, at high pressures, tor example, up to about 200 atmospheres, or at pressures intermediate thereof. Low pressures are advantageous under circumstances where carbon monoxide-containing gases are available at low pressure in that these gases may be employed without the necessity of compression. However, carbon monoxide-containing gases may be readily produced at high pressure by partial oxidation and employed at the pressure at which produced in the disintegration step of this process. The use of relatively high pressures elects substantial reduction in the size of the equipment required because of the resultant reduced gas volumes and the increased rates of the disintegration reactions. Accordingly, pressures within the range of about to 40 atmospheres are preferred.

An advantage of the process of thisinvention is that a substantial amount of grinding is avoided in ore beneciation.

Another advantage of the process of this invention is that the metal values may be readily separated from the ore gangue by means employing the different characteristics of the distintegrated particles.

Another advantage is that the particles produced may be readily transported employing the lluidized solids technique, the metal concentrate may be used in the form of fine particles, or the concentrate may :be readily agglomerated to form aggregates of beneliciated ore.

Another advantage of this process is that the metal component may be reduced at least in part in the beneciation step.

The accompanying drawing `diagrarnniatically illustrates an embodiment of the process of this invention. Although the drawing illustrates one embodiment of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus or materials described.

A raw ore from an external source not shown is received in bin 1. The raw ore is subjected to a preliminary size classication in grizzly 2 and the large lumps separated by the grizzly are passed to crusher 3. The fine material from the grizzly and the product of the Crusher are combined and passed to screen 4 to separate a fraction finer than about 40 mesh and a coarse fraction. The coarse fraction is passed to grinder 5 and the product returned to the screen 4 so that all material is ultimately ground to pass the 40 mesh screen. The fine fraction comprising ore having a particle size less than about 40 mesh is fed to disintegrator 6. Oxygen and natural gas are converted to synthesis gas containing about 2 mols of hydrogen and one mol of carbon monoxide in carbon monoxide generator 10. The partial combustion reaction which is effected in generator produces a temperature therein within the range of about 1800 to 3200 F. and it is preferred to maintain a partial combustion temperature within the range of about 2400 to 2800 F. The carbon monoxide-containing gas is passed into a lower portion of disintegrator 6 to supply heat to maintain the temperature therein within the range of about 650 to 1000 F. as well as to provide thedesired atmosphere containing carbon monoxide. Disintegration of the metal component of the ore is eliected without materially affecting the particle size of the gangue. By virtue of the resulting dilTerence in particle size, the relatively ne metal components are elutriated from the uidized bed by entrainment in the uidizing gas and are withdrawn from an upper portion of disintegrator 6 in a stream of the gas. The gas and suspended solids are passed to `a cyclone separator 11 to separate the gas from the beneiciated ore. The gas thus separated may be employed for other uses not shown, for example, for the reduction of metal ores. The beneiiciated ore may be further processed by known means for thel separation of the metal values. Coarse gangue particles are continuously withdrawn from a lower portion of the distintegrator to a stripper or elutriator 12. In stripper 12 the coarse particles lare passed in countercurrent contact with a stream of stn'pping gas which maybe a portion of'the carbon monoxidecontaining gas produced in generator 10, so. that only coarse particles of gangue are withdrawn from stripper 12 and line particles containing metal components are separated and entrained in the stripping gas and returned together to the disintegrator vessel.

Advantageously, etlluent gas from disintegrator 6 may be recycled to the disintegrator gasy inlet to supplement the carbon monoxide-containing gas employed thereby by recycle means not shown. Such recycle means may include means to scrub the recycle gas with a solvent which is selective for carbon dioxide, for example water or diethanol amine, to maintainthe concentration of carbon monoxide ata desired level.

The process of the invention is illustrated in the following example:

One. ton of Minnesota taconite consisting of about 60% silica gangue and 40% iron oxidesis crushed to pass a100 mesh screen. The crushed taconite-is charged to a fluid bed reaction zone maintained at a temperature of 700 F. and a pressure of p.s.i.g. A gas comprising substantially equal parts of carbon monoxide and hydrogen prepared by the partial oxidation ofY a heavy hydrocarbon oil is passed through the fluid bed reaction zoneat a superficial velocity of about 1.5 feet per second. Seven hundred and forty pounds of an iron ore concentrate are elutriated from the fluidized bed. The iron ore concentrate, substantially all of which passes a 200 mesh sieve and about 75% of which passes a 325 mesh sieve, comprises iron oxides, iron carbides and metallic iron and contains less than 10% silica. Twelve hundred and sixty pounds of residue are withdrawn `from the iluidized reaction zone. oxides.

Obviously many modifications and variations of the invention as hereinbefore set forthrrnay be made without departing fromthe spirit and scope thereof and only such limitations should ybe imposed as are indicated in the appended claims.

I claim:

l. A process for beneciating an oxidic iron ore con.

sisting of iron oxide and gangue comprising grinding said ore to form iluidizable orerparticles consisting of oxide and gangue; feeding said ore particles into a treating' chamber; fluidizing said ore particles by feeding a stream. of gas comprising carbon monoxide intofa lower portion of said treating chamber and maintaining a supercial gas velocity of 0.5 to 5 feet per second therein,

whilermaintaining said treating chamber and the ore particles therein at a temperature between 650 and 1000"l F., said carbon monoxide reacting with the oxide con-` gas from an upper portion of said treating chamber along withl said relativelyne particles of iron oxide entrained,

therein; and withdrawing said relatively coarse gangue particles from a lower portion of said treating chamber.

2. A process in -accordance with claim 1, also corn-- prisingpassing a stripping stream ofgas comprising carbon monoxide in countercurrent contact with said relativelyi The residue contains lessV than 10% iron,

oxide together into said treating chamber.

References Cited in the le of this patent UNITED STATES PATENTS Bradley July 5, 1932 1 Royster Nov. 7, 1950 6 Cyr et al. Dec. 9, 1952 Nelson Oct. 19, 1954 Lewis June 21, 1955 Ogorzaly Apr. 17, 1956 Giusti et al. Jan. 20, 1959 Johnson Ian. 20, 1959 FOREIGN PATENTS Great Britain June 24, 1946 Great Britain Apr. 6, 1948 

1. A PROCESS FOR BENEFICIATING AN OXIDIC IRON ORE CONSISTING OF IRON OXIDE AND GANGUE COMPRISING GRINDING SAID ORE TO FORM FLUIDIZABLE ORE PARTICLES CONSISTING OF OXIDE AND GANGUE, FEEDING SAID ORE PARTICLES INTO A TREATING CHAMBER, FLUIDIZING SAID ORE PARTICLES BY FEEDING A STREAM OF GAS COMPRISING CARBON MONOXIDE INTO A LOWER PORTION OF SAID TREATING CHAMBER AND MAINTAINING A SUPERFICIAL GAS VELOCITY OF 0.5 TO 5 FEET PER SECOND THEREIN, WHILE MAINTAINING SAID TREATING CHAMBER AND THE ORE PARTICLES THEREIN AT A TEMPERATURE BETWEEN 650 AND 1000* F., SAID CARBON MONOXIDE REACTING WITH THE OXIDE CON. STITUENT THEREOF, WHEREBY IS FORMED A PRODUCT CONSISTING TO SELECTIVELY DISINTEGRATE SAID OXIDE CONSTITUENT OF SAID ORE PARTICLES WITHOUT MATERIALLY AFFECTING THE GANGUE CONSTITUENT THEREOF, WHEREBY IS FORMED A PRODUCT CONSISTING ESSENTIALLY OF RELATIVELY FINE IRON OXIDE PARTICLES AND RELATIVELY COARSE GANGUE PARTICLES, WITHDRAWING A STREAM OF GAS FROM AN UPPER PORTION OF SAID TREATING CHAMBER ALONG WITH SAID RELATIVELY FINE PARTICLES OF IRON OXIDE ENTRAINED THEREIN, AND WITHDRAWING SAID RELATIVELY COARSE GANGUE PARTICLES FROM A LOWER PORTION OF SAID TREATING CHAMBER. 